The plugin selectively blurs the color information (both hue and saturation) in image. There are two basic scenarios / reasons to use this: When saturating poorly saturated images (to prevent artifacts in color) and cartoonizing images. The plugin blurs selectively, and can even "sharpen" transitions between two colors.
The plugin have thee basic outputs - blur the color on place/image, cartoon mode and creation of lines.
Additional features is saturation (three levels available) and so named forced blurring, this in fact under some conditions ignore tresholds given by an user.
Location in gimp: FILTERS -> BLUR -> COLOR SELECTIVE BLUR
See http://code.google.com/p/selective-color-blur/wiki/Introduction for more info & examples